Tonight (Feb. 20) sees the conclusion of
"Castle's" latest two-part extravaganza, as Beckett and Castle try to figure out a weakness in the U.S. economy that could mean the downfall of the country in "Lynchpin."

While the stakes don't seem as high as, say, Season 3's "Countdown," when Beckett and Castle defused a dirty bomb, the fact that the CIA is involved makes the case pretty high-pressure for the pair.

When
Jennifer Beals' Sophia Turner (
Castle's ex and the inspiration for Clara Strike) finds out that the partners chased a lead in the case without telling her, she doesn't take it very well. Guess Sophia doesn't find Rick's "going rogue" schtick as cute as Beckett does.

And, in case you missed it, check out "Pandora," part one of Beals' guest arc,
here.